Wax refining process



Patented June 9, 1953 Willem-Martin. Maz'e and Anna Berta Sweet,

Amsterdam, -.Neth'erlands', ass'ig'a'mors s 116A Shell 7-" DvelopmentqCQmp'any, L'Eineryvfile, Cafii., a r o atien o mlw re Hel fire wing. App ication July .21, 1952, ,,Serial This invention relettes- 1761 ?a. method: oflitreating lparr'aflin wax, particularly to 's'eparateithene'e f romn undesirable .aomponents in a liquid state, as by sweating;

waxwsweat'ing is one of. theoldestprocesses in the petroleumvindustry.lanai i employed to separate 'oil,.isoparaffins ancwther;nelativelyvlow-i melting, undesirable t constituents .zfrom' crude parafiin wax (slack Wax) ='in: pmerLtoHprepare purified paraffin :waxxconsistingwholly:01 princip'ally' of normal. parafiinihyd-rodarbonsfl 'Thetcmdeparafiin wax subjectecl to the .siive'st-v ing process usually; though not, necessarily; comes from-filter presses, wherea large p'arlt of .theeoil originallypresent-J11: the. ,crudeapara'ffin-wax removed,

Generally; the :crude waxis melted, apouredlnto pans or trays'with perfpratedhottoms and cooled theremntil the paralflin wax .hasibecomee solid cakes This sake is then, ;-graduai1ly reheated. :so. thatha liquid separates off which.rcontainsgoil and ,low melting ,isoparafiins-pr otherlmaite'rials, the presence of which is .undesirableairr, thetpu-rifled.- parafiinflwax; in addition,- a quantity; ELI/he normal paraffin ,waxesdesired in the: end, ,pIQdr: uct islusually found in,,thi;sliquid. The sweat inst; netr e i nalnm ltin as liter ly ms stepped at .3 the .point when the, wax, is sires-from 2,412 OVerSWeQt-tHe-eaKe ver tfirwi tl'r toelpply an intensive recircul y sin eotherwise the final product" will cofifiain acoinpgratively large amount of isoparaflins', For various applications; such as in the paper industry, the isopsraffi-n' eontent' of. a; parelflin was, shduld-bloWf A further clisaldvantageeonneetell with the presently employed sweating proessesis the long period Of tim "requirewfdr'swedw ing the'wax." Furthermore, in'the known-sweat i'ng processes; it'ls virtussll y only possible to sweat a par'ofiinwax with a relativelfwide b range. If-fi't-is desired "to prepare lubricating" oils with a, narrow boiling rang-e, paraifi witna narrow b'oiling'range' will sl ob b; tallied; this paraflin "wax" Cannot, hoWier," be eiieetively sweit'ed according to the-presently known processes;

In theknown sweating processes heat is sup plied directly or indirectly: to the waxbailf "by means of-warm water, warm air, or steam as by heating,-tubesimbddediin the wajxl, 'I hese tubes are present in a the trays in: I Whioh lie the wix cakes .tobextreated. Sometimestlre' wax cakes are placed in; a-chamber-or timneLwh-ieh is heeitefi throughout-lo .t'he; sweating temperatures 1 13-- oil. or; alternatively;- when a sample drawn from.

the sweateclwax shows lthat thezwax lias' readied the;melting point desinedl' It; should-, be, noted; here that; "the quall-my;-- 10f, the end product. is; better according; as; the 10H; content and the ,content ofisopamfii'ns orzrelae, ti-vely; low melting Lconstituen-ts; is; smaller; fini-z thermore the liquid. ,fiowlng w.ofiyshgmld contain as; few suitable inormalspanafilni Jhydroeanbonsas possible, I: For certain qualities iof- ,parafiin, waxe o-pa e l.p penqufl x.nparamneewaxfthesmi mumsm t n ip i tpf t en malma raffinwaxes which are perm-ittegl ln-the endepnoduqt is otten sei at ahqut 402 0.

h re; a e sm tsi saq ntases att whedlv Q-the we ti ls s s a r sent p ied i pracs pa rtpf the.suitable;,nonmalsparafifin waxessencl lip-in the-v sweated10ut-,'liquidlphasen, Asha lie: sult of-thisfilarg'e quantities of-lthis liquid phase haveto be-Lrecirculatedsdr retreated :ordentligt a sutficient economical yiem df tlie suitael parafifi-n waxes is obtained; thismeans; that the equipment-for carrying I out the process is large and expensive ancl the process its'li is relaitivef 1y costly." In order" to dbtasin e jfifial p qclu't with -a low isdpar-afin content it isnecessar y to quired-n-i' It is an :objeet of-thisl'inventionto provide-a sweatingiprocessswhereby ashighei 'field t heretofore, Npossilole Lof l the normali walxes msyi be; gobtained Itsi's-a; further: objectoofstni P vention to provide a process whereimthetpuri ty of slthe finarl, pro duet,. especially: .with. mega-ditto o e-ll w content 0flow melting ;isopamflins,wis

fl Jetl e li-onlthe-nwaxecake during *5 swea specifically, it has now beeri tha if, the wax, pakeijs; healtedsatpa raltealgoqt (W215 and- 0.975" pen, lite ,texnpergture ,rzin; ;ev ,ifrom i, about-e90." rF-yWh e.m ll eininsa echan cal ten-t e w sp iwfi-- stw imlawn l und l e W nshs ss th V d gher degree ,of

3 the described improvements, the possibility of channeling between the individual wax crystals is substantially avoided. Moreover, the maintenance of a critically limited pressure on the cake is such that the skeleton formed by the individual wax crystals is substantially maintained without being crushed by excessive pressure. In the event that excessive pressure is employed the wax skeleton collapses, thereby trapping oil or low melting isoparaflin waxes which are more desirably eliminated during the sweating period. If, on the other hand, no pressure other than normal atmospheric pressure is employed, the original pore volume is increased substantially by the voids created during removal of sweated fractions. By the term original pore volume is meant the pore volume occupied by non-crystalline hydrocarbons at'the initial temperature of sweating, that is, the volume of the liquid constituents present in the paraffin wax, constituting oil and substances dissolved therein. It will be understood that as low melting wax fractions are sweated from the wax cake the pore volume will increase unless suitable steps are taken to maintain the original pore volume. By maintaining the original pore volume is meant the act of controlling the original pore volume to within about of that originally found in the cake at the commencement of sweating. In other words, the pore volume is maintained so as to be either increased or decreased by not more than about 10% of the original space, by a controlled compression of the wax cake, balancing the increase in the pore volume to within 10 of the original pore volume.

In maintaining the original pore volume within this relatively narrow limit mechanical pressure is applied to the cake, either in the form of a mechanical ram or alternatively by means of a solvent for the non-waxy fractions in direct contact with the parafiin wax. In this latter case this may comprise low molecular weight aliphatic alcohols such as butanol (or other monohydric alcohols having from l to 6 vention the original pore volume is maintained .by. the. above described means until at least about 90% of the constituents to be sweated have been removed from the cake. At that time or thereafter pressure may be increased if desired so as to crush the wax skeleton to its minimum volume for storage convenience or more eflicient handling. Higher purity is obtained, however, if the critical pressure range is maintained until at least 95% of the constituents to be sweated have been removed from the wax cake.

As the examples given hereinafter show,the

I combination of the critically limited process carbon atoms per molecule) which act at the working temperature as a solvent for the constituents to be removed from the paraflin .wax but which have little or no such eifect on the solid paraffin wax. Low molecular weight ketones such as methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, etc. may be used.

Sweating is preferably carried out as suggested hereinbefore in a vessel with a perforated bottom such as pan type screens. These latter vessels may be fitted with a ram to be employed as the pressure means either alone or together with a liquid such as that referred to above.

The success of the present process depends not only upon the maintenance of the original pore volume by means of restricting pressure to a critically limited range, but also upon raising the temperature of the wax cake during sweating at a rate which is relatively critically narrow. As stated hereinbefore, this rate of heating the cake during the sweating should be between about 0.025 and 0.075 F. per minute. Preferably the rate of heating is maintained between about 004 and 006 F. per minute.

Still more preferably this rate of heating is utilized in conjunction with a preferred pressure on the cake of between about 1 and about 10 pounds per square inch. Optimum results are obtained if the original pore volume isl varied by not more than about 5% I conditions described. above cause a substantial increase in the yield of desirable parafiin wax and a substantial decrease in the oil content of the final product. Conversely, it will be. found that the sweated constituents contain a correspondingly small amount of desirable par' affin wax constituents.

In carrying out the process of the present invention the following steps are desirable: The crude wax is melted and poured in the usual manner into a tray having a perforated bottom. This charge is then cooled, preferably Until the point of transition is reached it is advisable that cooling take place slowly. Thereafter, however, it is preferred to cool the wax quickly. By cooling slowly to the point of transition, i. e., until crystallization has just finished, complete or almost complete and close packed crystallization takes place of those com ponents which form the solid phase. This solid phase constitutes the skeleton of the sweated wax cake. Due to the rapid cooling subsequent to the slow cooling during the transition range, many minute cracks occur in the crystallized mass causing it to become morepermeable to the sweated oils and low melting waxes which are removed thereafter.

When cooling has been carried out to the point at which a substantially completely solid mass has been formed, heat and pressure areapplied to the cake in accordance with the con ditions described hereinbefore, thereby heating the wax at a rate between about 0.025 and about 0.075" F. per minute within the temperature range of about and about Fl whilemaintaining the pressure between about 0.3 and about 15 pounds per square inch, so as to substantially maintain the original pore volume of the cake. Under these conditions sweating takes place at a relatively rapid rate te pered. w th e de sw a i prq s s as it; is prefer'a-ble to allow the temperature from ---beg-inning 'toe'nd of the'wtratment to increase atet -relatively uniformrate; -preferably' slowly hroughout-" 'the- 'entire- -sweating peri'od.

The eXamples'wh'iclfifollow itlustrate the*ad-- vantages to" 'b e*--gained* by the 1 usebf themon- "r 'ditions described hereinbefore*-as cons'tituting thelimits' of *the present 'invention.

.iExampZe I "The *prccess- 'according 'to the invention was -'=compare'cl"- to' the existing' method bfsweating in which ipressure' is not:'=:ap'plied. .l-:Al Venezuelan para-frinwax with' an oil-"content oi"16% by-weig'ht and an-isoparaifin content'o'f about'2'5 %:-by weight served -as'"base materialb his marafiinwv'axfi was subjected to" asweating tre'atrnent "l'a'stir'ig fi hours, during which the temperature wa'sraised from 983- FLv'to 1319 1 -The parafiin wax was containeddna vesselwwith ape'rforated bottom, and

the pressure was exerted by means of a ram fitting..:ti'ght1yjin'lthewessel.

The results-rwerei as iollows:

Yield of paraffin Wax in percent (wt) 36 49 Oil content of the sweated paraifin wax in percent (\vt.) 5 0. 95

The melting point of the parafiin wax obtained in the sweating process according to the invention was 59 C.

By using the existing process no suitable finished product could be obtained in the stated time, while by working according to the invention a high quality paraffin wax was prepared.

If the initial paraffin wax is pressed at the indicated pressure and at room temperature, no oil can be removed.

Example II Similar experiments were carried out using as a base an Indonesian paraffin wax (oil content 18% by weight, isoparafiin content about 12% by weight), in which the temperature was raised from'1l5 to 133 F. The sweating process lasted 7 hours.

At a pressure of 1 lb./in'. on the parafiin rialremamed -sciid;-

\ -means' 'of amanlilfittingitightl results were as'lfollows or ting-pointot'the s wax i 1"T-Wclaim as'oui' invention: a I

'1 .In a? m'ethodfot sweating a predominalfitly H .par'arfinwax to separatetheiefromlundsirable m 1.con'stituent's Iinith' liiifiidiphasef the' site'psfbmprising preparing .the waxllcaketfor sweatingliby v cooling a molten .paralifin wax. ina .prforat'ed re- :ceptacl'eeto a temperature-mi which a solid wax cake is formed, said solid comprising ai. -wax l-skeleton being associated. withM-an,.originaldpore volume, lthe latter.abeingi initially ..occiipied4.lby liquid constituents at iii thefcommenceinnti of sweating, ande-raisingl the-temperatureof.-i said. .-:-cake ;a t a ratet-between about .0259; and-labout 0.075? per minute within artemperature range between about90%and aboutl150% while-mainattaining tar-mechanicalpressure on the .wax cake of: :between about .0.3' 'andabout lwpoundseper "isquara inch;- whereby the; original moreJvolume .otthe wax-cakeis yariedyby hombres-than about 10.% .until: at 'least- 90 of the 'sweated-.-constitu .s-entsiiarerremotvedtfromitheicake.

:za 2:211'1- a. method: of sweating a predominantly .ir paraflin :waxuto Iseparate theref-nom undesirable constituents .inthe eliquid aphase;l-the stepswomprising preparing the wax cake for sweatingaby :.cooling, 2, -molten!para-11in waxtin ia =-peraforated reai-zceptaclerto axtemperatureiat whichaa sclidtwax cake is formed, said solid comprising a wax skeleton being associated with an original pore volume, the latter being intitially occupied by liquid constituents at the commencement of sweating, and raising the temperature of said cake at a rate between about 0.04" and about 0.06 F. per minute within a temperature range between about 90 and about 150 F. while maintaining a mechanical pressure on the wax cake of between about 0.3 and about pounds per square inch, whereby the original pore volume of the wax cake is varied by no more than about 10% until at least 90% of the sweated constituents are removed from the cake.

3. In a method of sweating a predominantly paraflin wax to separate therefrom undesirable constituents in the liquid phase, the steps comprising preparing the wax cake for sweating by cooling a molten parafiln wax in a perforated receptacle to a temperature at which a solid Wax cake is formed, said solid comprising a wax skeleton having an original pore volume, the

latter being-initially occupied by liquid constituents at the commencement of sweating, and raising the temperature of said cake at a rate between about 0.025 and about 0.0'75 F. per minute within a temperature range between about 90 and about 150 F. while maintaining a mechanical pressure on the wax cake of between about 1 and about 10 pounds per square inch, whereby the original pore volume of the wax cake is varied by no more than about 10% until at least 90% of the sweated constituents are removed from the cake.

4. In a method of sweating a predominantly paraflln wax to separate therefrom undesirable constituents in the liquid phase, the steps comprising preparing the wax cake for sweating by cooling a molten parafiin wax in a perforated receptacle to a temperature at which a solid wax cake is formed, said solid comprising a wax skeleton having an original pore volume, the latter being initially occupied by liquid constituents at the commencement of sweating, and raising the temperature of said cake at a rate between about 0.025 and about 0.075 F. per minute within a temperature range between about 100 and about 135 F. while maintaining a mechanical pressure on the wax cake of between about 0.3 and about 15 pounds'per square inch, whereby the original pore volume of the wax cake is varied by no more than about 10% until at least 90 of the sweated constituents are removed from the cake.

5. In a method of sweating a predominantly paraffin wax to separate therefrom undesirable constituents in the liquid phase, the steps comprising preparing the wax cake for sweating by cooling a molten parafiin wax in a perforated receptacle to a temperature at which a solid wax cake is formed, said solid comprising a wax skeleton having an original pore volume, the latter being initially occupied by liquid constituents at the commencement of sweating, and raising the temperature of said cake at a rate between about 0.025 and about 0.075 )3. per minute within a temperature range between about 90 and about 150 F. while maintaining a mechanical pressure on the wax cake of between about 0.3 and about 15 pounds per square inch, whereby the original pore volume of the wax cake is varied by no more than about 5% until at least 95% constituents in the liquid phase, the stepscomprising preparing the wax cake for sweating by cooling a molten paraffin wax in a perforated receptacle to a temperature at which a solid wax cake is formed, said solid comprising a wax skeleton having an original pore volume, the latter being initially occupied by liquid constituents at the commencement of sweating, and raising the temperature of said cake at a rate between about 0.025 and about 0.075 F. per minute within a temperature range between about 90 and about -150 F. while maintaining a mechanical ram on the wax cake with a pressure between about 0.3 and about 15 pounds per square inch, whereby the original pore volume of the wax cake is varied by no more than about 10% until at least I 90% of the sweated constituents are removed ents at the commencement of sweating, and raisof the sweated constituents are removed from the 5 ing the temperature of said cake at a rate between about 0.025 and about 0.075 F. per minute within a temperature range between about and about F. while maintaining a liquid pressure on the wax cake of between about 0.3 and about 15 pounds per square inch, whereby the original pore volume of the wax cake is varied by no more than about 10% until at least 90% of the sweated constituents are removed from the cake, said liquid being substantially a nonsolvent for wax constituents retained in the wax cake and being a solvent for the sweated constituents to be removed from said cake under the temperature and pressure conditions of the sweating operation.

WILLEM MARTIN MAZEE. ANNA BARTA SWART.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,636,730 Amdursky July 26, 1927 2,230,079 Hanson et al. July 28, 1941 2,305,024 Moyer Dec. 15, 1942 

1. IN A METHOD OF SWEATING A PREDOMINANTLY PARAFFIN WAX TO SEPARATE THEREFROM UNDERSIRABLE CONSTITUENTS IN THE LIQUID PHASE, THE STEPS COMPRISING PREPARING THE WAX CAKE FOR SWEATING BY COOLING A MOLTEN PARAFFIN WAX IN A PERFORATED RECEPTACLE TO A TEMPERATURE AT WHICH A SOLID WAX CAKE IS FORMED, SAID SOLID COMPRISING A WAX SKELETON BEING ASSOCIATED WITH AN ORIGINAL PORE VOLUME, THE LATTER BEING INITIALLY OCCUPIED BY LIQUID CONSTITUENTS AT THE COMMENCEMENT OF SWEATING, AND RAISING THE TEMPERATURE OF SAID CAKE AT A RATE BETWEEN ABOUT 0.025* AND ABOUT 0.075* F. PER MINUTE WITHIN A TEMPERATURE RANGE BETWEEN ABOUT 90* AND ABOUT 150* F. WHILE MAINTAINING A MECHANICAL PRESSURE ON THE WAX CAKE OF BETWEEN ABOUT 0.3 AND ABOUT 15 POUNDS PER SQUARE INCH, WHEREBY THE ORIGINAL PORE VOLUME OF THE WAX CAKE IS VARIED BY NO MORE THAN ABOUT 10% UNTIL AT LEAST 90% OF THE SWEATED CONSTITUENTS ARE REMOVED FROM THE CAKE. 